1. Field of the Invention
The invention relates to field of disk drives and more particularly to magnetic disk lubricants.
2. Description of the Related Art
Hard disk drives record data on hard, rotating magnetic disks. A hard disk typically comprises a hard substrate upon which are deposited one more or thin films that are used to record and retain the data in the form of magnetic domains. These magnetic domains in turn generate magnetic flux in a predetermined direction that can be sensed by sensors of various kinds including so-called magnetoresistive sensors. In a hard disk drive, the magnetic sensor is caused to fly very close to the magnetic disk—so close that intermittent contact can be expected. As a result the magnetic recording layers are typically covered with a carbon overcoat layer that is in turn lubricated with a lubricant.
These lubricants reduce stiction and friction between the head and the carbon overcoat. They also fill in microscopic gaps in the carbon overcoat to protect the magnetic alloy from corrosion. However, the lubricants typically used in hard disk drives degrade over time leading at times to disk drive failure either because of carbon overcoat wear or because of corrosion.
It has recently been discovered that the use of ultraviolet light to “cure” these lubricants improves both the reliability and tribological performance of the lubricant. Lubricant performance increases until a certain UV dosage has been reached, after which there is no further improvement in lubricant performance. In a particular example, this “saturation” level is reached in approximately 3 minutes of exposure in a system where Fomblin® Z-DOL, available from Ausimont USA, with an X1P additive, available from the Dow Chemical Company, is exposed to a mercury discharge UV lamp at a power density of 35 milliwatts per square cm.
However, this exposure time is excessively long in the manufacture of hard disks. Improvements in process time are required to make UV exposure practicable in the manufacture of magnetic hard disks.